The neutron beam therapy facility at Fermilab is designed to study the efficacy of relatively high energy neutrons in controlling human cancer of a type which is likely to be resistant to conventional photon beams. For this purpose the accelerated proton beam in the 200 MeV linac at the Laboratory is deflected periodically during that part of the work cycle in which the accelerator is normally on standby condition, and transported onto a beryllium target. Protons with an energy of 66 MeV are used for this purpose. A well collimated beam has been obtained, our RBE values have been determined, and OER of 1.6 has been derived from the study of a variety of radiobiological test systems. Randomized clinical trails have been to designed test the efficacy of this beam on advanced epidermoid carcinomas of the head and neck, brain tumors, carcinoma of the cervix and bladder cancer, in conjunction with existing clinical neutron beam therapy facilities here in the United States. Protocols for studying the efficacy of neutrons in the management of lung cancer, osteogenic sarcomas, connective tissue sarcomas, and inoperable breast cancer are being developed.